Elevated platelet activating factor in the tracheal aspirate at birth and signs of intra-uterine inflammation in infants with neonatal pulmonary emphysema

To investigate the pathophysiology of the neonatal pulmonary emphysema, we assayed platelet activating factor (PAF) in the tracheal aspirates of the low birth weight infants. A total of 29 neonates (birth weight <1750 g) who required mechanical ventilation were enrolled. Tracheal aspirates were obtained within 48 h and blood samples collected within 24 h of life. PAF was assayed on the basis of its ability to cause aggregation of washed rabbit platelets. PAF was significantly elevated in four infants who showed pulmonary emphysema within the 1st week of life (median 24 pg/g lipid phosphorus, range 9.9–200) compared with those detected in the other three groups of infants; infants with respiratory distress syndrome (RDS) in whom chronic lung disease (CLD) did not develop (median 1.8 pg/g lipid phosphorus, range 0–30; P < 0.05), infants without RDS nor CLD (median 0.64 pg/g lipid phosphorus, range 0–14; P < 0.05) and infants with other types of CLD (median 1.1 pg/g lipid phosphorus, range 0–1.8; P < 0.01). The four infants who developed pulmonary emphysema within the 1st week of life, had significantly elevated serum IgM and neutrophilia at birth. The increased amount of PAF in the tracheal aspirates shows the presence of inflammation in the lung at birth. The elevated serum IgM level and neutrophilia indicate that the inflammation begins in utero. Conclusion Our data suggest that neonatal pulmonary emphysema is caused by intra-uterine inflammation increasing platelet activating factor in the lungs. Platelet activating factor may play a role in aggravating the process of pulmonary emphysema. Received: 20 July 1998 / Accepted: 14 February 1999